The invention relates to a method for providing an inorganic coating to ammonium nitrate-based particles, in particular to ammonium nitrate-based particles for use as a fertilizer. Such inorganic coating is suitable for providing macronutrients, micronutrients or a combination thereof to a particulate fertilizer.
Plants may obtain macronutrients, micronutrients or any combination thereof, amongst others, by the application of particulate fertilizers. Macronutrients are typically divided into primary nutrients (nitrogen, phosphorus, sulphur and potassium) and secondary nutrients (calcium, magnesium, and sulfur). Micronutrients (also referred to as trace elements) include boron, chlorine, copper, iron, manganese, molybdenum, and zinc.
As a first object, the invention is directed to the provision of an inorganic coating, suitable for providing micronutrients to a particulate fertilizer.
As a second object, the invention is directed to the provision of an inorganic coating, suitable for providing macronutrients, micronutrients or any combination thereof to a particulate fertilizer.
At present, there exist different possibilities to provide particulate fertilizers with macronutrients, micronutrients or a combination thereof.
A first possibility is to add macronutrients, micronutrients or a combination thereof into the fertilizer during the manufacturing process of the fertilizer particles, for instance before the fertilizer particles are formed. The disadvantage of this possibility is that some reactions between the added macro- or micronutrient components and the acids or other materials present may render some of the macro- or micronutrients unusable. When for instance zinc oxide (ZnO) comes into contact with phosphoric acid (H3PO4), insoluble Zn3(PO4)2 is formed rendering the macro- or micronutrients unusable.
A second possibility is to coat the macro- or micronutrients on the fertilizer particles using a non-aqueous solution of the macro- or micronutrients, for instance an oil-based solution to which magnesium oxide (MgO2), zinc oxide (ZnO), boric oxide (B2O3), another mineral alkaline or any combination thereof is added. However, addition of oil to the particulate fertilizer results in dilution of the fertilizer. The fertilizer particles furthermore become sticky and having a reduced flowability. Also, by using an oil in the coating, the amount of carbon is raised, consequently raising the explosion sensitivity of the particulate fertilizer.
A third possibility is to physically blend the fertilizer particles with specific particles of macro- or micronutrients. In that case, a blend is obtained often having particles with a different size, resulting in segregation of the particles. When spreading such a blend on the field by the farmer, a non-uniform distribution of the added nutrients is obtained.
A fourth possibility is to form an aqueous solution of the macro- or micronutrients and spraying these on the fertilizer particles. When applying said aqueous solution on hygroscopic particles such as ammonium nitrate (AN) particles, these particles will absorb the water of the aqueous solution, resulting in the free flowing fertilizer particles to swell, degrade, or in the worst case, turn into a wet mud.